23-07-2012, 03:29 PM
Power stability
Power stability .doc (Size: 393 KB / Downloads: 28)
INTRODUCTION
Power stability in developing countries creates the need for automation of phase selection or alternative sources of power to back-up the utility supply. Most industrial and commercial applications are dependant on power supply and if the process of change over is manual, not only considerable time is wasted but also the device or machine may get damaged from human error during the change over connections, incurring massive losses.
Here we are presenting a automatic phase selector that can be installed in residential and office premises where single phase equipments are used. When any of the mains phase line fails, it automatically selects the available phase line. (Out of three phase lines or backup lines.) By using 89C51 we can display which phase is available and which phase is connected to the LOAD through microcontroller.
Micro-controller 89C51 :
It is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash Programmable and Erasable Read Only Memory (PEROM). The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the MCS-51™ instruction set and pin-out. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer.
Phase Sensor Block :-
This block senses the phase. For sensing the phase we are using PT (Potential Transformer) which converts 230 Vac into 12 Vac. The output of PT is given to rectifier. The rectifier will convert AC into DC. This DC has some AC ripples, So Capacitor filter is used to remove the AC ripples. The output of filter is pure DC 12 volts. But microcontroller requires only + 5Vdc. Therefore we are using zener of 5 volts.
Power Supply :-
For our project we require + 5 Volt and + 12 Volt supply. + 5 Volt is required for phase sensor and microcontroller board. And + 12 Volt supply is required to drive Relay.
LCD display :-
LCD display is used to display the status of phase whether phase available or not. i.e phase is present or absent.
For our project we require 16 X 2 LCD display.